This application relates to a nonvolatile memory device, and more particularly, to a nonvolatile memory cell with a high speed write operation, a nonvolatile memory device, and a method of programming the nonvolatile memory device.
Semiconductor memory devices storing data may be roughly classified into volatile memory devices and nonvolatile memory devices. Volatile memory devices lose stored data when the supply of power is cut off whereas nonvolatile memory devices retain stored data even when the supply of power is cut off.
Examples of volatile memory devices include dynamic random access memories (DRAMs) and static random access memories (SRAMs). Examples of nonvolatile memory devices include flash memories and phase random access memories (PRAMs). DRAMs can read and write data in less than 100 ns, and SRAMs can read and write data in less than 50 ns. Although DRAMs are faster than SRAMs in terms of read and write operations, the DRAMs require periodic refreshing due to their volatility, thereby consuming a lot of power.
Flash memories can read data in less than 100 ns. But flash memories are generally slower than other types of memories in performing write operations. For example, NAND flash memories write data in less than 200 μs, and NOR flash memories write data in less than 10 μs. PRAMs can read data in less than 100 ns, but PRAMs write data in a time range between about 100 ns to 1 μs. Since flash memories are fast in a read operation but are slow in a write operation, a lot of time is taken to program the flash memories. However, flash memories do not require refreshing due to their nonvolatility.